BIGRLZ

I like it I'm about to drop a LS1 out of a 2003 Suburban into my 79 Firebird, I had a 400 in it I also have a Q-jet off the 400 & 600 CFM carb I might have to try the Q-jet. If there anything that you can help me with hit me up.
Thanks

onefast84

Its all about knowing how to tune them they are a totally different beast from a holley. I used to work for a guy that could tune a q to runn with any holley!

Beeterolds

Basically you can't expect a Q-Jet off a big engine with a lower power band to perform the same on a smaller engine with a higher power band..

In my case I got lucky.. A took basically a stock Q-jet off a 350 Vette motor and tossed it on a motor thats only 25 cubes smaller but has a better combustion chamber and different power band.. It seems to work perfect.. I need to get a wide band 02 to really dial it in but as it sits right now it runs badass.. 2nd gear pull from 40 on up is amazing the carb doesnt miss a beat.

NoSloZ_1

I'm having horrible luck with my 750 mechanical secondary on my stock 5.3 in my s10. I have a q-jet laying around and after reading this I think I will buy the adapter and throw it on and see what happens.

ZONES89RS

iTrader: (25)

I don't want to be a a hole, but it is a duh factor, a 750 mechanical, wide open on a 5.3 in a car with not large converter that has some weight is not going to perform as you wish. A 650 DP maybe, but not a 750. A 750 vacuum secondary would be fantastic. If you have a spare a jet, try it, or sell the 750/trade for a VS.

NoSloZ_1

Yea had I known that in the beginning that's what I would have bought. My plans are a big cam and 243s eventually so I bought the carb with the intentions of doing all that. But for right now with stock internals, its definitely not a good choice.

NoSloZ_1

Edit: actually zone, at wide open throttle it runs hard. It's the part throttle cruising and acceleration that really sucks. It misses and bogs at about 1/4 throttle. So you either have to barely give it any throttle or give it over half. It's a pain for daily driving.

ZONES89RS

iTrader: (25)

It is out of tune as well, the mid range throttle is where i had issues as well on a 5.3 with a cam and my mechanical 750 off my 89 RS with the 6.0, the 3000 converter was not enough to help either.

NoSloZ_1

Yea that's why I think I'm just gonna throw the q jet on it for now while its still stock. Seems a better option at this point.

3pedals

iTrader: (3)

I say you invest in a wideband O2, then you will have some VALUABLE feedback in order to tune it to run as good as it possibly can, no matter what parts you throw at it.
Barrett

Beeterolds

As Ive said I had great luck using a Q-jet off a motor with similar displacement and compression.. A stock 5.3 using a Q found on a stock 9.0 350 would get you close to where you need to be... My point is dialing one of these carbs in from scratch is a bitch no matter what..

A Q found on a 305 might suit a 4.8 better as well as a carb found off a 400 or 403 Olds might be close in the ball park for a 6.0.. Just a thought.. My opinion is not law just from what I've experienced..

Also mentioned before if your running a wild cam a Q-jet probably wouldnt be a good carb for that application because they so depend on the all important vacuum signal from the motor..

NoSloZ_1

Well I threw the q jet I had on my truck tonight. I think it needs rebuilt. It's squeeling super loud and running like crap. I'm thinking its a loud vacuum leak but have yet to trace it. Ran out of time tonight. I did drive around the block and it ran better except for the inconsistent idle and loud noise.

Beeterolds

I wonder where the squealing is coming from... Thats odd.. My Q-jet hisses like a sumbitch but from what ive gathered thats how most sound with an open air cleaner..

NoSloZ_1

Yea I have no idea where it came from either. I took it off and replaced it with an identical one and now it runs perfect! I couldn't an happier. Now my biggest problem is traction. Haha

Beeterolds

Hell ya.. It would be nice if someone made an intake with a spreadbore mounting boss.. but that almost seems unreasonable..

RPM WS6

iTrader: (3)

Agreed.

I think the small primaries of the spreadbore Q-jet makes it easier for people to toss one on and get decent part throttle performance, and also good driveability on a street engine with little effort. Holleys need to be sized properly (even in VS format, IMO) to give crisp part throttle manners, and they rarely just drop on and perform their best. You really need to work with a Holley out of the box to get best results; usually they will run if you just toss them on, but you'll never get ideal performance without some adjustments. There is a lot of mis-information on Holley tuning that leads people down a path of frustration and poor results, and then this leads to people posting about how "holleys are junk, POS, etc.". If Holleys really were all hopeless junk, then how can you explain all the cars that run well with them? It's all in the tuning.....same as with any fuel delivery setup.

ZONES89RS

iTrader: (25)

Yea, I have been lucky and dropped them on and also had to spend a day getting them in the ball park. But I do run a VS on my 4.8 with zero issue. I am going to try a edelbrock on my 4.8 going in my 91 RS to see if I can get over 25 MPG out of it and **** off the efi guys that simply refuse to believe a carb can get decent economy.

1981TA

iTrader: (7)

I'm aiming for 20 MPG on mine, but then my carb might be a bit big. I put a 800 CFM Edelbrock Thunder AVS on. Still needs tuning (which seems pretty straight-forward), but it sure is fun

The wide band O2 sensor helps big time.

hifi875

iTrader: (2)

recomendations on a wideband? Only thing i don't like about my setup is it stinks when i start it in the garage etc. Ive tried getting the smell cleaned up by adjusting using a vacum gauge, but I probly need to check jetting too.

RPM WS6

iTrader: (3)

Main jets won't have any effect on how it smells (or runs) at idle. If you don't have cats, it's always going to smell some. If you have a cam with a lot of overlap, it's going to smell even more. This is still the case even with a perfectly tuned EFI setup. Verifying your jetting with a wideband is a good thing, but this isn't going to clean up the idle any further.